diff --git a/src/Umbraco.Cms.ManagementApi/Controllers/Security/BackOfficeController.cs b/src/Umbraco.Cms.ManagementApi/Controllers/Security/BackOfficeController.cs
index 74ce67ed032a..219ce30e78a2 100644
--- a/src/Umbraco.Cms.ManagementApi/Controllers/Security/BackOfficeController.cs
+++ b/src/Umbraco.Cms.ManagementApi/Controllers/Security/BackOfficeController.cs
@@ -2,14 +2,19 @@
 using Microsoft.AspNetCore;
 using Microsoft.AspNetCore.Authentication;
 using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Options;
 using OpenIddict.Abstractions;
 using OpenIddict.Server.AspNetCore;
 using Umbraco.Cms.Core;
+using Umbraco.Cms.Core.Configuration.Models;
 using Umbraco.Cms.Core.Security;
 using Umbraco.Cms.Web.BackOffice.Security;
 using Umbraco.Extensions;
 using Umbraco.New.Cms.Web.Common.Routing;
+using SignInResult = Microsoft.AspNetCore.Mvc.SignInResult;
+using IdentitySignInResult = Microsoft.AspNetCore.Identity.SignInResult;
 
 namespace Umbraco.Cms.ManagementApi.Controllers.Security;
 
@@ -21,12 +26,18 @@ public class BackOfficeController : ManagementApiControllerBase
     private readonly IHttpContextAccessor _httpContextAccessor;
     private readonly IBackOfficeSignInManager _backOfficeSignInManager;
     private readonly IBackOfficeUserManager _backOfficeUserManager;
+    private readonly IOptions<SecuritySettings> _securitySettings;
 
-    public BackOfficeController(IHttpContextAccessor httpContextAccessor, IBackOfficeSignInManager backOfficeSignInManager, IBackOfficeUserManager backOfficeUserManager)
+    public BackOfficeController(
+        IHttpContextAccessor httpContextAccessor,
+        IBackOfficeSignInManager backOfficeSignInManager,
+        IBackOfficeUserManager backOfficeUserManager,
+        IOptions<SecuritySettings> securitySettings)
     {
         _httpContextAccessor = httpContextAccessor;
         _backOfficeSignInManager = backOfficeSignInManager;
         _backOfficeUserManager = backOfficeUserManager;
+        _securitySettings = securitySettings;
     }
 
     [HttpGet("authorize")]
@@ -41,36 +52,93 @@ public async Task<IActionResult> Authorize()
             return BadRequest("Unable to obtain OpenID data from the current request");
         }
 
+        return request.IdentityProvider.IsNullOrWhiteSpace()
+            ? await AuthorizeInternal(request)
+            : await AuthorizeExternal(request);
+    }
+
+    private async Task<IActionResult> AuthorizeInternal(OpenIddictRequest request)
+    {
+        // TODO: ensure we handle sign-in notifications for internal logins.
+        // when the new login screen is implemented for internal logins, make sure it still handles
+        // user sign-in notifications (calls BackOfficeSignInManager.HandleSignIn) as part of the
+        // sign-in process
+        // for future reference, notifications are already handled for the external login flow by
+        // by calling BackOfficeSignInManager.ExternalLoginSignInAsync
+
         // retrieve the user principal stored in the authentication cookie.
         AuthenticateResult cookieAuthResult = await HttpContext.AuthenticateAsync(Constants.Security.BackOfficeAuthenticationType);
-        if (cookieAuthResult.Succeeded && cookieAuthResult.Principal?.Identity?.Name != null)
+        var userName = cookieAuthResult.Succeeded
+            ? cookieAuthResult.Principal?.Identity?.Name
+            : null;
+
+        if (userName != null)
         {
-            BackOfficeIdentityUser? backOfficeUser = await _backOfficeUserManager.FindByNameAsync(cookieAuthResult.Principal.Identity.Name);
+            BackOfficeIdentityUser? backOfficeUser = await _backOfficeUserManager.FindByNameAsync(userName);
             if (backOfficeUser != null)
             {
-                ClaimsPrincipal backOfficePrincipal = await _backOfficeSignInManager.CreateUserPrincipalAsync(backOfficeUser);
-                backOfficePrincipal.SetClaim(OpenIddictConstants.Claims.Subject, backOfficeUser.Key.ToString());
-
-                // TODO: it is not optimal to append all claims to the token.
-                // the token size grows with each claim, although it is still smaller than the old cookie.
-                // see if we can find a better way so we do not risk leaking sensitive data in bearer tokens.
-                // maybe work with scopes instead?
-                Claim[] backOfficeClaims = backOfficePrincipal.Claims.ToArray();
-                foreach (Claim backOfficeClaim in backOfficeClaims)
-                {
-                    backOfficeClaim.SetDestinations(OpenIddictConstants.Destinations.AccessToken);
-                }
+                return await SignInBackOfficeUser(backOfficeUser, request);
+            }
+        }
+
+        return DefaultChallengeResult();
+    }
+
+    private async Task<IActionResult> AuthorizeExternal(OpenIddictRequest request)
+    {
+        var provider = request.IdentityProvider ?? throw new ArgumentException("No identity provider found in request", nameof(request));
+
+        ExternalLoginInfo? loginInfo = await _backOfficeSignInManager.GetExternalLoginInfoAsync();
+        if (loginInfo?.Principal != null)
+        {
+            IdentitySignInResult result = await _backOfficeSignInManager.ExternalLoginSignInAsync(loginInfo, false, _securitySettings.Value.UserBypassTwoFactorForExternalLogins);
 
-                if (request.GetScopes().Contains(OpenIddictConstants.Scopes.OfflineAccess))
+            if (result.Succeeded)
+            {
+                // Update any authentication tokens if succeeded
+                await _backOfficeSignInManager.UpdateExternalAuthenticationTokensAsync(loginInfo);
+
+                // sign in the backoffice user associated with the login provider and unique provider key
+                BackOfficeIdentityUser? backOfficeUser = await _backOfficeUserManager.FindByLoginAsync(loginInfo.LoginProvider, loginInfo.ProviderKey);
+                if (backOfficeUser != null)
                 {
-                    // "offline_access" scope is required to use refresh tokens
-                    backOfficePrincipal.SetScopes(OpenIddictConstants.Scopes.OfflineAccess);
+                    return await SignInBackOfficeUser(backOfficeUser, request);
                 }
-
-                return new SignInResult(OpenIddictServerAspNetCoreDefaults.AuthenticationScheme, backOfficePrincipal);
+            }
+            else
+            {
+                // avoid infinite auth loops when something fails by performing the default challenge (default login screen)
+                return DefaultChallengeResult();
             }
         }
 
-        return new ChallengeResult(new[] { Constants.Security.BackOfficeAuthenticationType });
+        AuthenticationProperties properties = _backOfficeSignInManager.ConfigureExternalAuthenticationProperties(provider, null);
+        return new ChallengeResult(provider, properties);
     }
+
+    private async Task<IActionResult> SignInBackOfficeUser(BackOfficeIdentityUser backOfficeUser, OpenIddictRequest request)
+    {
+        ClaimsPrincipal backOfficePrincipal = await _backOfficeSignInManager.CreateUserPrincipalAsync(backOfficeUser);
+        backOfficePrincipal.SetClaim(OpenIddictConstants.Claims.Subject, backOfficeUser.Key.ToString());
+
+        // TODO: it is not optimal to append all claims to the token.
+        // the token size grows with each claim, although it is still smaller than the old cookie.
+        // see if we can find a better way so we do not risk leaking sensitive data in bearer tokens.
+        // maybe work with scopes instead?
+        Claim[] backOfficeClaims = backOfficePrincipal.Claims.ToArray();
+        foreach (Claim backOfficeClaim in backOfficeClaims)
+        {
+            backOfficeClaim.SetDestinations(OpenIddictConstants.Destinations.AccessToken);
+        }
+
+        if (request.GetScopes().Contains(OpenIddictConstants.Scopes.OfflineAccess))
+        {
+            // "offline_access" scope is required to use refresh tokens
+            backOfficePrincipal.SetScopes(OpenIddictConstants.Scopes.OfflineAccess);
+        }
+
+        return new SignInResult(OpenIddictServerAspNetCoreDefaults.AuthenticationScheme, backOfficePrincipal);
+    }
+
+    private static IActionResult DefaultChallengeResult() => new ChallengeResult(Constants.Security.BackOfficeAuthenticationType);
 }